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6lo                                                          Lijo Thomas
Internet-Draft                                                     C-DAC
Intended status: Standards Track                               P. Akshay
Expires: September 14, 2017                  Indian Institute of Science
                                                      Satish Anamalamudi
                                         Huaiyin Institute of Technology
                                                             S.V.R.Anand
                                                            Malati Hegde
                                             Indian Institute of Science
                                                              C. Perkins
                                                               Futurewei
                                                          March 13, 2017


            Packet expiration time in 6LoWPAN Routing Header
                   draft-lijo-6lo-expiration-time-02

Abstract

   This document specifies a new type to the 6LoWPAN Dispatch Page 1 for
   carrying the expiration time of data packets within the 6LoWPAN
   routing header.  The expiration time is useful in making forwarding
   and scheduling decisions for time critical IoT M2M applications that
   need deterministic delay guarantees over constrained networks and
   operate within time-synchronized networks.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 14, 2017.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.




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   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents
   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
   2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  6LoRHE Generic Format . . . . . . . . . . . . . . . . . . . .   3
   4.  Deadline-6LoRH Description  . . . . . . . . . . . . . . . . .   3
   5.  Deadline-6LoRH Format . . . . . . . . . . . . . . . . . . . .   4
   6.  Deadline-6LoRH in Three Network Scenarios . . . . . . . . . .   6
     6.1.  Scenario 1: Endpoints in the same DODAG (N1) in non-
           storing mode. . . . . . . . . . . . . . . . . . . . . . .   6
     6.2.  Scenario 2: Endpoints in Networks with Dissimilar L2
           Technologies. . . . . . . . . . . . . . . . . . . . . . .   7
     6.3.  Scenario 3: Packet transmission across different DODAGs
           (N1 to N2). . . . . . . . . . . . . . . . . . . . . . . .   8
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   9
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  10
   9.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  10
   10. References  . . . . . . . . . . . . . . . . . . . . . . . . .  10
     10.1.  Normative References . . . . . . . . . . . . . . . . . .  10
     10.2.  Informative References . . . . . . . . . . . . . . . . .  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  12

1.  Introduction

   Low Power and Lossy Networks (LLNs) are likely to be employed for
   implementing real time industrial applications that require end-to-
   end delay guarantees [I-D.grossman-detnet-use-cases].  A
   Deterministic Network typically requires that data packets generated
   by the senders have to reach the receivers within strict time bounds.
   Intermediate nodes use the expiration time information to make
   appropriate packet forwarding and scheduling decisions to meet the
   time bounds.

   The draft [I-D.ietf-roll-routing-dispatch] specifies the 6LoWPAN
   Routing Header (6LoRH), compression schemes for RPL routing (source
   routing) operation [RFC6554], header compression of RPL Packet
   Information [RFC6553], and IP-in-IP encapsulation.  This document
   specifies a new Deadline-6LoRH type to the 6LoWPAN Dispatch Page 1,



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   so that the expiration time of data packets can be included within
   the 6LoWPAN routing header.  In addition, this specification
   specifies handling of the expiration time when packets traverse
   through time-synchronized networks operating in different timezones
   or distinct reference clocks.

2.  Terminology

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
   "OPTIONAL" in this document are to be interpreted as described in
   [RFC2119].

3.  6LoRHE Generic Format

   The generic header format of the 6LoRHE is specified in
   [I-D.ietf-roll-routing-dispatch].  Figure 1 describes the 6LoRHE
   generic format.

      0                   1
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-             ...               -+
     |1|0|1| Length  |      Type     |                                 |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-             ...               -+
                                      <--          Length           -->

                          Figure 1: 6LoRHE format

   1.  Length: In Figure 1, Length of the 6LoRHE expressed in bytes,
       excluding the first 2 bytes.  This enables a node to skip a
       6LoRHE that it does not support and/or cannot parse, for instance
       if the Type is not recognized.

   2.  Type: Type of the 6LoRHE.

   3.  Length: variable

4.  Deadline-6LoRH Description

   The Deadline-6LoRH (see Figure 2) is an elective 6LoRH that provides
   a compressed form of expiration time for an IPv6 datagram.  Along
   with the expiration timer, the header can include the packet
   origination time, to enable a close estimate of the total delay
   incurred by a packet.

   The packet expiration time field contains the value of the packet
   expiration time.  The packet SHOULD be delivered to the Receiver
   before this time.



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      packet_expiration_time = packet_origination_time + max_delay

   All nodes within the network SHOULD process the Deadline-6LoRH in
   order to support delay-sensitive deterministic applications.  In this
   specification, the packet origination time is represented in
   microseconds or milliseconds according to a scaling parameter value
   in the routing header.  In the case of a time slotted synchronized
   network where a global time is maintained in the units of slot
   lengths of certain resolution, the origination time is converted from
   the current time into microseconds or milliseconds.  A 6tisch minimal
   network [I-D.vilajosana-6tisch-minimal] is such a network, where the
   slot duration is typically 10msec, and the global time is given as
   ASN (Absolute Slot Number).

   The delay experienced by packets in the network is a useful metric
   for network diagnostics and performance monitoring.  To support this
   feature, the specification provides an optional packet Origination
   Time field as part of the header which is initialized by the sender
   using the current clock time of the outgoing network interface
   through which the packet is forwarded.  Whenever the packets crosses
   over to a network using a different reference clock, the Origination
   Time field is updated to represent the same Origination Time but
   using the reference clock of the outgoing interface into the new
   network.  This is the same as the current time when the packet is
   transmitted into the new network, minus the delay already experienced
   by the packet, say 't'.  In effect, to the newly entered network, the
   packet will appear to have originated 't' time units earlier with
   respect to the reference clock of the new network.

   Origination Time in new network = current_time_in_new_network -
                  delay_already_experienced_in_previous_network(s)

5.  Deadline-6LoRH Format

        0               1               2
        0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |1|0|1| Length  |  6LoRH Type   |O|D| ER|ETL| OR| OTL |Rsv| EXP |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |      ET (variable length)     | OT(variable length)(optional) |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                      Figure 2: Deadline-6LoRH format

   Length (5 bits): Length represents the total length of the Expiration
   Time type measured in octets.

   6LoRH Type: TBD



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   O flag (1bit): Indicates the presence of Origination Time field.  '1'
   means the Origination Time is present, and '0' means it is absent.

   D flag (1 bit): The 'D' flag, set by the Sender, indicates the action
   that needs to be taken when an 6LR detects expiration time is
   elapsed.  If 'D' bit is 1, then the 6LR SHOULD drop the packet if the
   expiration time is elapsed.  If 'D' bit is 0, then the 6LR MAY ignore
   the Expiration Time and forward it.

   ER (2 bits) Indicates time units for packet expiration time field:

      00 : Expiration time represented in microseconds
      01 : Expiration time represented in milliseconds
      10 : Expiration time represented in seconds
      11 : User defined

   ETL (3 bits): Length of Expiration Time field.

   For example, if the expiration time is represented in microseconds
   ETL = 000 means the expiration time in the 6LoRHE is 1 octet (8 bits)
   long.  Similarly, Length = 111 means the expiration time is 8 octets
   (64 bits) long.

   OR (2 bits) : Indicates time units for Packet Origination Time:

      00 : Expiration time represented in microseconds
      01 : Expiration time represented in milliseconds
      10 : Expiration time represented in seconds
      11 : User defined

   OTL (3 bits) : Length of Origination Time field.

   Rsv (2 bits) : Reserved

   EXP (3 bits) : Multiplication factor expressed as exponent of 2.

   The value of the ET field is multiplied by 2 to this power, to get
   the actual expiration time in the units represented by ER.  The
   default value of EXP is 000, so that the ET field is unaffected.

   ET Value (0..64-bit) : Expiration Time value

   OT Value (0..64-bit) : Origination Time value

   Whenever the Sender initiates the IP datagram, it includes the
   Deadline-6LoRH along with other 6LoRH information.





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   Example: consider a 6TiSCH network with time-slot length of 10ms.
   Let the current ASN when the packet is originated be 200, and the
   maximum allowable delay (max_delay) for the packet delivery is 1
   second from the packet origination, then:

      expiration_time = packet_origination_time + max_delay

         = 200*10ms + 1 second
         = 3 * 10^6 microseconds

   This expiration time requires 22 bits in the worst case, or 3 octets.
   Better compression can be achieved by using a combination of OR and
   EXP bit fields.

6.  Deadline-6LoRH in Three Network Scenarios

   In this section, Deadline-6LoRH operation is described for 3 network
   scenarios.  Figure 3 depicts a constrained time-synchronized LLN that
   has two subnets N1 and N2, connected through LBRs
   [I-D.ietf-6lo-backbone-router] with different reference clock times
   T1 and T2.

                          +-------------------+
                          | Time Synchronized |
                          |      Network      |
                          +---------+---------+
                                    |
                                    |
                                    |
                     +--------------+--------------+
                     |                             |
                  +-----+                       +-----+
                  |     | Backbone              |     | Backbone
             o    |     | router                |     | router
                  +-----+                       +-----+
             o                  o               o
                 o    o   o               o  o   o  o   o  o
            o      LLN    o                 o  LLN   o  o
               o   o    o      o             o o o     o  o
         6LoWPAN Network (subnet N1)   6LoWPAN Network (subnet N2)

                 Figure 3: Intra-network Timezone Scenario

6.1.  Scenario 1: Endpoints in the same DODAG (N1) in non-storing mode.

   In scenario 1, shown in Figure 4, the Sender 'S' has an IP datagram
   to be routed to a Receiver 'R' within the same DODAG.  For the route
   segment from Sender to 6LBR, the Sender includes a Deadline-6LoRH by



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   encoding the expiration time contained in the inband-OAM header
   extension.  Then 6LR begins hop-by-hop operation to forward the
   packet towards the 6LBR.  Once 6LBR receives the IP datagram, it
   generates a IPv6-in-IPv6 encapsulated packet when sending the packet
   downwards to the Receiver [I-D.ietf-roll-useofrplinfo].  The 6LBR
   copies the Deadline-6LoRH from the Sender originated IP header to the
   outer IP header.  The Deadline-6LoRH contained in the inner IP header
   is elided.

                              +-------+
                   ^          | 6LBR  |       |
                   |          |       |       |
                   |          +-------+       |
           Default |      (F)/      /| \      | IP-in-IP
           routing |     /  \      / |  \     |      Encapsulation
                   |    /    \   (C) |  (D)   |
                   |  (A)    (B) /   | / |\   |
                   |  /|\     |\:   (E)  : R  |
                     S : :    :     / \       V

             Figure 4: End points within same DODAG(subnet N1)

   At the tunnel endpoint of IPv6-in-IPv6 encapsulation, the Deadline-
   6LoRH is copied back from the outer header to inner header, and the
   inner IP packet is delivered to 'R'.

6.2.  Scenario 2: Endpoints in Networks with Dissimilar L2 Technologies.

   In scenario 2, shown in Figure 5, the Sender 'S' (belonging to DODAG
   1) has IP datagram to be routed to a Receiver 'R' over a time-
   synchronized IPv6 network.  For the route segment from 'S' to 6LBR,
   'S' includes a Deadline-6LoRH.  Subsequently, 6LR will perform hop-
   by-hop operation to forward the packet towards the 6LBR.  Once the IP
   datagram reaches 6LBR of DODAG1, it encodes the expiration time (and,
   if available, the origination time) into the In-band OAM header
   extension, [I-D.brockners-inband-oam-data] and passes the datagram to
   the IPv6 layer for further routing.














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                              +----------------+
                              | Time           |
                              | synchronized   |------R
                              | Network        |
                              +----------------+
                                      |
                                      |
                            ----------+-----------
                     ^                |
                     |            +---+---+
                     |            | 6LBR  |
            Default  |            |       |
             routing |            +------++
                     |        (F)/      /| \
                     |       /  \      / |  \
                     |      /    \   (C) |  (D)
                       :  (A)    (B) /   | / |\
                          /|\     |\:   (E)  :
                         S : :    :     / \
                                       :   :

      Figure 5: Packet transmission in Dissimilar L2 Technologies or
                                 Internet

   The IP datagram is routed to another time synchronized deterministic
   network following its own distinct reference clock, so the expiration
   time in In-band OAM has to be updated according to the measurement of
   the current time in the new network.

6.3.  Scenario 3: Packet transmission across different DODAGs (N1 to
      N2).

   Consider the scenario depicted in Figure 6, in which the Sender 'S'
   (belonging to DODAG 1) has an IP datagram to be sent to Receiver 'R'
   belonging to another DODAG (DODAG 2).  The operation of this scenario
   can be decomposed into combination of case 1 and case 2 scenarios.
   For the route segment from 'S' to 6LBR, 'S' includes the Deadline-
   6LoRH.  Subsequently, each 6LR will perform hop-by-hop operation to
   forward the packet towards the 6LBR.  Once the IP datagram reaches
   6LBR1 of DODAG1, it applies the same rule as described in Case 2
   while routing the packet to LBR2 over a (likely) time synchronized
   wired backhaul.  The wired side of LBR2 can be mapped to receiver of
   Case 2.  Once the packet reaches LBR2, it updates the Deadline-6LoRH
   by adding the current time of DODAG2.  Further, it generates an IPv6-
   in-IPv6 encapsulated packet when sending the packet downstream to the
   Receiver [I-D.ietf-roll-useofrplinfo].





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                     Time Synchronized Network
                  -+---------------------------+-
                   |                           |
      DODAG1   +---+---+                   +---+---+   DODAG2
    Instance 1 | 6LBR1  |                  | 6LBR2 | Instance 2
               |       |                   |       |     |
               +-------+                   +-------+     |
           (F)/      /| \              (F)/      /| \    |
          /  \      / |  \            /  \      / |  \   |
         /    \   (C) |  (D)         /    \   (C) |  (D) |IP-in-IP
       (A)    (B) /   | / |\       (A)    (B) /   | / |\ | Encapsulation
       /|\     |\:   (E)  : :      /|\     |\:   (E)  : :|
      S : :    :     / \          : : :    :     / \     |
                    :   :                       :   R    V
   Network N1, time zone T1      NetWork N2, time zone T2

        Figure 6: Packet transmission in different DODAGs(N1 to N2)

   Consider an example of a 6TiSCH network in which S in DODAG1
   generates the packet at ASN 200 to R in DODAG2.  Let the maximum
   allowable delay be 1 second.  The time-slot length in DODAG1 and
   DODAG2 is assumed to be 10ms.  Once the expiration time is encoded in
   Deadline-6LoRH, the packet is forwarded to LBR of DODAG1.  Suppose
   the packet reaches LBR of DODAG1 at ASN 250.

   current_time = ASN at LBR * slot_length_value

   remaining_time = expiration_time - current_time

   = ((packet_origination_time + max_delay) - current time)

      = (200*10 ms + 1 second) - 2.5 seconds
      = 0.5 second
      = 5 * 10^5 microseconds.

   The remaining time is encoded in In-Band OAM (see Case 2) and
   forwarded to LBR2 over a different L2-interface, typically wired.
   Once the packet reaches LBR2, the expiration time in Deadline-6LoRH
   is adjusted by adding or subtracting the difference between the
   reference clocks of the two networks, before forwarding the packet to
   its connected 6TiSCH network.

7.  IANA Considerations

   This document defines a new 6LoWPAN Timestamp Header Type, and
   assigns a value (TBD) from the 6LoWPAN Dispatch Page1 number space.





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                        6LoRH Type      Value
                   +------------------+--------+
                   | Deadline-6LoRH   | TBD    |
                   +------------------+--------+

                       Figure 7: Deadline-6LoRH type

8.  Security Considerations

   The security considerations of [RFC4944], [RFC6282] and [RFC6553]
   apply.  Using a compressed format as opposed to the full in-line
   format is logically equivalent and does not create an opening for a
   new threat when compared to [RFC6550], [RFC6553] and [RFC6554].

9.  Acknowledgements

   The authors thank Pascal Thubert for suggesting the idea and
   encouraging the work.  Thanks to Shwetha Bhandari's suggestions which
   were instrumental in extending the timing information to
   heterogeneous networks.  The authors acknowledge the 6TiSCH WG
   members for their inputs on the mailing list.  Special thanks to
   Jerry Daniel,Shalu Rajendran, Seema Kumar, Avinash Mohan and Anita
   Varghese for their support and valuable feedback.

10.  References

10.1.  Normative References

   [I-D.ietf-roll-routing-dispatch]
              Thubert, P., Bormann, C., Toutain, L., and R. Cragie,
              "6LoWPAN Routing Header", draft-ietf-roll-routing-
              dispatch-05 (work in progress), October 2016.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC4944]  Montenegro, G., Kushalnagar, N., Hui, J., and D. Culler,
              "Transmission of IPv6 Packets over IEEE 802.15.4
              Networks", RFC 4944, DOI 10.17487/RFC4944, September 2007,
              <http://www.rfc-editor.org/info/rfc4944>.

   [RFC6282]  Hui, J., Ed. and P. Thubert, "Compression Format for IPv6
              Datagrams over IEEE 802.15.4-Based Networks", RFC 6282,
              DOI 10.17487/RFC6282, September 2011,
              <http://www.rfc-editor.org/info/rfc6282>.




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   [RFC6550]  Winter, T., Ed., Thubert, P., Ed., Brandt, A., Hui, J.,
              Kelsey, R., Levis, P., Pister, K., Struik, R., Vasseur,
              JP., and R. Alexander, "RPL: IPv6 Routing Protocol for
              Low-Power and Lossy Networks", RFC 6550,
              DOI 10.17487/RFC6550, March 2012,
              <http://www.rfc-editor.org/info/rfc6550>.

   [RFC6553]  Hui, J. and JP. Vasseur, "The Routing Protocol for Low-
              Power and Lossy Networks (RPL) Option for Carrying RPL
              Information in Data-Plane Datagrams", RFC 6553,
              DOI 10.17487/RFC6553, March 2012,
              <http://www.rfc-editor.org/info/rfc6553>.

   [RFC6554]  Hui, J., Vasseur, JP., Culler, D., and V. Manral, "An IPv6
              Routing Header for Source Routes with the Routing Protocol
              for Low-Power and Lossy Networks (RPL)", RFC 6554,
              DOI 10.17487/RFC6554, March 2012,
              <http://www.rfc-editor.org/info/rfc6554>.

10.2.  Informative References

   [I-D.brockners-inband-oam-data]
              Brockners, F., Bhandari, S., Pignataro, C., Gredler, H.,
              Leddy, J., Youell, S., Mizrahi, T., Mozes, D., Lapukhov,
              P., and R. <>, "Data Formats for In-situ OAM", draft-
              brockners-inband-oam-data-02 (work in progress), October
              2016.

   [I-D.grossman-detnet-use-cases]
              Grossman, E., Gunther, C., Thubert, P., Wetterwald, P.,
              Raymond, J., Korhonen, J., Kaneko, Y., Das, S., and Y.
              Zha, "Deterministic Networking Use Cases", draft-grossman-
              detnet-use-cases-01 (work in progress), November 2015.

   [I-D.ietf-6lo-backbone-router]
              Thubert, P., "IPv6 Backbone Router", draft-ietf-6lo-
              backbone-router-03 (work in progress), January 2017.

   [I-D.ietf-roll-useofrplinfo]
              Robles, I., Richardson, M., and P. Thubert, "When to use
              RFC 6553, 6554 and IPv6-in-IPv6", draft-ietf-roll-
              useofrplinfo-11 (work in progress), March 2017.

   [I-D.vilajosana-6tisch-minimal]
              Vilajosana, X. and K. Pister, "Minimal 6TiSCH
              Configuration", draft-vilajosana-6tisch-minimal-00 (work
              in progress), October 2013.




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Authors' Addresses

   Lijo Thomas
   C-DAC
   Trivandrum  695033
   India

   Email: lijo@cdac.in


   P.M. Akshay
   Indian Institute of Science
   Bangalore  560012
   India

   Email: akshaypm@ece.iisc.ernet.in


   Satish Anamalamudi
   Huaiyin Institute of Technology
   No.89 North Beijing Road, Qinghe District
   Huaian
   China

   Email: satishnaidu80@gmail.com


   S.V.R Anand
   Indian Institute of Science
   Bangalore  560012
   India

   Email: anand@ece.iisc.ernet.in


   Malati Hegde
   Indian Institute of Science
   Bangalore  560012
   India

   Email: malati@ece.iisc.ernet.in










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   Charles E. Perkins
   Futurewei
   2330 Central Expressway
   Santa Clara  95050
   Unites States

   Email: charliep@computer.org












































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